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# Copyright (C) 2018 Bloomberg LP 

# 

# Licensed under the Apache License, Version 2.0 (the "License"); 

# you may not use this file except in compliance with the License. 

# You may obtain a copy of the License at 

# 

# <http://www.apache.org/licenses/LICENSE-2.0> 

# 

# Unless required by applicable law or agreed to in writing, software 

# distributed under the License is distributed on an "AS IS" BASIS, 

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 

# See the License for the specific language governing permissions and 

# limitations under the License. 

 

 

""" 

DiskStorage 

================== 

 

A CAS storage provider that stores files as blobs on disk. 

""" 

 

import logging 

import os 

import tempfile 

 

from .storage_abc import StorageABC 

 

 

class DiskStorage(StorageABC): 

 

def __init__(self, path): 

self.__logger = logging.getLogger(__name__) 

 

if not os.path.isabs(path): 

self.__root_path = os.path.abspath(path) 

else: 

self.__root_path = path 

self.__cas_path = os.path.join(self.__root_path, 'cas') 

 

self.objects_path = os.path.join(self.__cas_path, 'objects') 

self.temp_path = os.path.join(self.__root_path, 'tmp') 

 

os.makedirs(self.objects_path, exist_ok=True) 

os.makedirs(self.temp_path, exist_ok=True) 

 

def has_blob(self, digest): 

self.__logger.debug("Checking for blob: [{}]".format(digest)) 

return os.path.exists(self._get_object_path(digest)) 

 

def get_blob(self, digest): 

self.__logger.debug("Getting blob: [{}]".format(digest)) 

try: 

return open(self._get_object_path(digest), 'rb') 

except FileNotFoundError: 

return None 

 

def delete_blob(self, digest): 

self.__logger.debug("Deleting blob: [{}]".format(digest)) 

try: 

os.remove(self._get_object_path(digest)) 

except OSError: 

pass 

 

def begin_write(self, digest): 

return tempfile.NamedTemporaryFile("wb", dir=self.temp_path) 

 

def commit_write(self, digest, write_session): 

self.__logger.debug("Writing blob: [{}]".format(digest)) 

object_path = self._get_object_path(digest) 

 

try: 

os.makedirs(os.path.dirname(object_path), exist_ok=True) 

os.link(write_session.name, object_path) 

except FileExistsError: 

# Object is already there! 

pass 

 

write_session.close() 

 

def _get_object_path(self, digest): 

return os.path.join(self.objects_path, digest.hash[:2], digest.hash[2:])